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[Xen-users] present domU with 1 CPU with multiple cores

  • To: "xen-users@xxxxxxxxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: Jonathan Salomon <jonathan@xxxxxxxxxxxxx>
  • Date: Tue, 23 Jun 2009 11:29:51 +0300
  • Accept-language: en-US
  • Acceptlanguage: en-US
  • Delivery-date: Tue, 23 Jun 2009 01:30:44 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: Acnz3MbiKr+s+D4iQ1GJnhrdYib6Nw==
  • Thread-topic: present domU with 1 CPU with multiple cores

Hi all,


I have a machine with 2 physical CPUs with each 2 cores and as such when I do cat /proc/cpuinfo on Dom0 it reports 4 CPUs. I want to run a couple of DomU instances on this machine. However to make sure that Dom0 will always respond even when the DomU instances have a high load, I want to keep CPU 0 available only for Dom0. Therefore in the DomU config files I’m using the following CPU definition: cpus="1-3". Does it makes sense to do this? Or would Xen handle this better on its own?


Anyway, so one of the DomU instances runs software that I have bought a 1CPU license for. Consequently I have to set ‘vcpus=1’ otherwise it will tell me that I do not have a multiple CPU license. However it is ok to have 1 CPU with multiple cores. Therefore to speed it up I was wondering how I can tell Xen to assign say 2 cores to this DomU instance, but present it as 1 CPU with 2 cores.


Also how do I see on which physical CPU a DomU instance is running? When I set cpus=”1-3” and vcpus=”1” , then ‘xm top’ will show that the instance is running on vCPU 0 (which I assume is CPU 0 of that instance, not physical CPU0 since I deliberately pinned it to CPUs 1-3). Also ‘xm list’ will show how many vCPUs that DomU runs on, but not on which physical CPU.




Best wishes,


Jonathan Salomon

IT Manager

Panaya Inc. – Cut 50% of your SAP upgrade cost with automation software.

Tel: +972 (0) 9 761 8007

Cell: +972 (0) 52 7335999

Fax: +972 (0) 9 746 7901

E-mail: jonathan@xxxxxxxxxxxxx

Web: www.panayainc.com


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